1. Field of the Invention
The present invention relates to a process for preparing quaternary ammonium compounds from a tertiary amine and an alkylating agent containing a hydroxy or a thio group and a halogen group on adjacent carbon atoms. More specifically, the subject invention is directed to a process for preparing quaternary ammonium compounds from a tertiary amine and an alkylating agent containing a hydroxy or a thio group and a halogen group on adjacent carbon atoms in the presence of an epoxy entraining reactant.
2. Description of the Prior Art
Quaternary ammonium compounds have many commercial uses such as fabric softeners, anti-static agents, detergents, wetting agents, emulsifying agents, germicides, fungicides, textile assistants, textile lubricants, corrosion inhibitors, lubricant additives, mold-release agents, chemical intermediates, catalysts and the like.
A growing concern in the use of quaternary ammonium compounds in the above applications lies in their stability. That is, these compounds are very stable, comprising as they typically do four alkyl groups attached to a nitrogen atom. The non-biodegradable nature of these compounds poses a serious environmental problem, their disposability. The use of biodegradable quaternary ammonium compounds suggests itself as a solution to this growing problem. Indeed, biodegradable quaternary ammonium compounds are known in the art. These compounds are characterized by the inclusion of ester, ether and/or hydroxy groups. Their use, however, has been discouraged by the absence of commercially viable methods for their synthesis. Thus, while quaternary ammonium compounds containing hydroxy groups have been prepared, no commercially acceptable method has been developed for synthesizing these compounds.
Those skilled in the art are aware that quaternary ammonium compounds provided with hydroxy or thio functionality are subject to hydrolysis and thus degradation. However, the addition of this functionality into quaternary ammonium compounds is provided by alkylating agents in which the alkylating group is provided with hydroxyl or thiol functionality. The problem associated with this reaction resides in the long period of time required for this reaction to occur and, even then, in the low yield of the desired quaternary ammonium compound.
These two problems, slow reaction and low yield, are independent of whether the quaternary ammonium compound is an intermediate or the desired compound. That is, it applies whether the alkylating agent containing the biodegradable functionality is provided on a long chain alkylating agent to directly form the final product or whether this functionality is included in a short chain alkylating agent which is later reacted, by methods well known in the art, with a long chain alkyl group to produce the final quaternary ammonium compound product.
Several references teach the formation of quaternary ammonium compounds from long chain alkylating agents provided with hydroxy, ester or ether functionality. U.S. Pat. Nos. 3,104,933; 3,636,114; 3,879,464 and 3,972,855 establish the thermodynamic feasibility of these reactions. However, an analysis of the rate and yield of these reactions alert those skilled in the art of the difficulties associated with commercialization of these reactions.
The use of catalysts have been suggested to overcome the deficiencies of the prior art processes for synthesizing quaternary ammonium compounds. Thus, a variety of catalysts have been advanced for the alkylation of secondary and tertiary amines to produce quaternary ammonium compounds. Suggested catalysts include sodium hydroxide (U.S. Pat. No. 3,932,495) and the combination of sodium hydroxide and sodium bicarbonate (U.S. Pat. No. 3,318,954).
The use of epoxides and epihalohydrins in the formation of quaternary ammonium compounds is known in the art. For example, alkylthiohydroxypropyl quaternary ammonium halides are obtained by simultaneously reacting stoichiometric amounts of an alkylmercaptan, an epihalohydrin and a tertiary amine. These reactions are conducted at elevated temperature and typically require 16-24 hours at reflux to obtain 50-90% conversion to the product.
The quaternary ammonium halides of U.S. Pat. No. 2,775,604 are prepared in two distinct steps by reacting a polyhydroxylic compound with an epihalohydrin in the presence of a Lewis acid catalyst. The resultant glycerol halohydrin ether of the polyhydroxylic compound is reacted with a tertiary amine at elevated temperature in the absence of a catalyst.
Epoxides are used to purify quaternary ammonium compounds by reaction therewith. U.S. Pat. No. 3,468,816 teaches that this purification is the result of reduction of amine contamination.
In U.S. Pat. No. 3,272,712 a hydroxyester quaternary ammonium is prepared by reacting equimolar amounts of a fatty acid salt, an epihalohydrin and a secondary amine to form a tertiary amine which is then quaternized with dimethylsulfate or the like.
In contrast to the foregoing disclosures, U.S. Pat. No. 3,342,840 relates to the formation of hydroxy ester quaternary ammonium compounds by reacting a glycidyltrialkyl ammonium halide, itself a reaction product of an epihalohydrin and a tertiary amine, with a fatty acid.
A multistep process for preparing quaternary ammonium compounds is disclosed in U.S. Pat. No. 3,932,495 wherein an alkylated alcohol is reacted with excess epichlorohydrin to yield a hydroxyether chloride which, after removal of excess epichlorohydrin, is reacted with a secondary amine in the presence of a base to produce a quaternary ammonium compound.
Japanese Patent No. 49-1510 discloses a method of preparation of a quaternary ammonium compound that contains ester linkages by mixing a fatty acid with a tertiary amine to form the salt and then adding epichlorohydrin to complete the reaction.
A different method to produce quaternary ammonium compounds having ether and/or ester functionality is described in U.S. Pat. No. 4,339,391. That method involves esterification of a fatty acid with a tertiary amine followed by quaternization with a lower alkyl group.
Another class of quaternary ammonium compounds, recently recognized as having improved properties over other quaternary ammonium compounds, bis-quaternary ammonium compounds, also have not been commercially exploited to the extent they should because of the absence of a commercially viable process. Bis-quaternary ammonium compounds, the subject of U.S. Pat. Nos. 4,734,777 and 4,812,263 among others, are characterized by the presence of two nitrogen atoms in the molecules. The compounds are reported to possess excellent surface active properties.
The above remarks establish the absence in the art of processes to produce quaternary ammonium compounds having hydroxy, ester and/or ether functionality at a rate and in a yield that makes it commercially possible to exploit the desirable properties of these compounds.